How Speed Layer Uses Real-User Data
Purpose
Explain how Speed Layer uses real user experience data to measure impact, guide optimization, and demonstrate results.
Why real user data matters
Real user data reflects what actual shoppers experience across:
- Different devices
- Different networks
- Different pages and journeys
This is the most reliable way to understand whether a site is improving for real visitors.
Google reference:
- Core Web Vitals overview https://web.dev/vitals/
Measuring active vs control
Speed Layer can be evaluated in two states:
- Active state: optimizations are running
- Control state: optimizations are not applied, so you can measure a baseline
RUM allows you to compare these states using the same real traffic patterns, rather than relying on a single lab run.
What to measure
Speed Layer measurement should focus on:
- Core Web Vitals (LCP, CLS, INP)
- Supporting metrics (FCP, TTFB)
- Breakdowns by device and page type
How to use the data
Focus on percentiles
Percentiles such as p75 are useful because they reflect typical user experience rather than best case sessions.
Segment by page type
Dealer sites have different performance profiles across:
- Homepage
- SRP
- VDP
- Lead forms
Compare like for like
When comparing active vs control:
- Use the same time window
- Segment by mobile vs desktop
- Compare the same page types
How it supports optimization
RUM helps identify:
- Which pages improved most
- Which device segments still struggle
- When third party changes introduce regressions
Related pages
- What Is RUM (Real User Monitoring)?
- Setting Baselines and Comparing Before/After
- Common Misreads of Performance Data (and How to Avoid Them)